Wavelength-dependent Gradients

of Photoinhibition of PS II

An option that the MICROFIBER-PAM offers is the investigation of gradients of photosystem II characteristics within the leaf. For such investigations, the pointed tip of a working fiber (MF-F) is advanced into the leaf tissue by a micromanipulator, and saturation pulse analysis is carried out at defined depths of penetration.

Using this strategy, Terashima and his colleagues have analyzed how strong light of different colors damages photosystem II at various distances from the leaf surface. By measuring the maximum photochemical quantum yield of photosystem II (FV/FM), the authors demonstrated that amplitude as well as leaf gradients of photoinhibition depend on the color of photoinhibitory light.

Intra-leaf profiles of FV/FM in leaves of Capsicum annuum measured by a MICROFIBER-PAM having an optical microfiber of 30 μm diameter. The micro fiber was inserted into the leaf tissues with the aid of a three-dimensional water-pressure micromanipulator (WR-60, Narishige, Tokyo, Japan). Prior to FV/FM measurements, leaf discs were treated with lincomycin, an inhibitor of protein synthesis, and then photoinhibited at 2000 μmol photons m-2 s-1 at room temperature for 60 min by broad-band blue (400–500 nm, blue symbols), or red light (600–700 nm, red symbols). Measurements with non-irradiated control disks are shown as open symbols. Data from Terashima I, Fujita T, Inoue T, Chow WS, Oguchi R (2009) Plant Cell Physiology 50: 684–697. Original data were kindly provided by Prof. Ichiro Terashima.